The invention relates to a form-fill-seal machine, particularly a form-fill-seal machine wherein a web of bag material, such as foil, before transforming it into a tubular shape, is provided with so-called zipper strips, one for each bag to be made/filled. Said zipper strips generally consist of two strip members situated opposite each other and provided with male and female parts that can be brought into detachable engagement with each other, are taken from a stock and are applied transverse to the web, either with or without a limited pre-weld or pre-adhesion. In the action of transverse sealing the bags, the zipper strip is also permanently welded to the bag walls.
From U.S. Pat. No. 4,617,683 it is known to apply a zipper strip provided with adjacent male and female parts, over the full width of a web of bag material, by engaging a leading area with a vacuum head and moving the head transverse over the upper side of the web to the other edge. Subsequently the zipper strip is welded to the web by means of a thermal seal rod extending from above and an anvil. Alternatively the zipper strip may be provided with a heat activated glue.
From U.S. Pat. No. 4,878,987 it is known to supply the cooperating male and female parts of the zipper strip from both sides, transverse to the web, by means of pusher rolls. The male and female strips are then each pushed from their side towards the center, guided by transverse ducts, and then welded to the web.
From the international patent application WO 98/03328 it is known to place a zipper strip transverse to the web of bag material by means of a vacuum band positioned above the web and weld the strip to the bag material.
Applying the zipper strips requires a high control of the orientation and the exact location of the strips, as imperfections in it may hinder the further process and may result in malfunctioning.
It is an object of the invention to provide a form-fill-seal machine of the type mentioned in the preamble with which a very high degree of control can be achieved in placing the zipper strips.
It is a further object of the invention to provide a form-fill-seal machine of the type mentioned in the preamble, with which a high processing speed can be realized of high accuracy.
From one aspect the invention to that end provides a form-fill-seal machine comprising means for moving a web of packaging material through the machine according to a process path and means for transforming the web into filled bags, furthermore comprising a zipper strip applicator device having means for supplying a zipper strip for each bag transverse to the process path, which supply means comprise a first and a second conveyor, which in the supply direction of the zipper strip are placed one behind the other and are both provided with means for retaining or engaging the zipper strip during supply, a cutting means such as a blade being placed between the first and the second conveyor for cutting the zipper strip and the first and the second conveyor being provided with their own first and second drive means.
The division into two conveyors makes it possible to divide functions as well, and namely a supply function for the first conveyor and a positioning function for the second conveyor, the zipper strip each time being held over his length by the first and/or second conveyor.
Preferably the machine is provided with control means for the first and second drive means and the blade, the control means being adjusted to consecutively operate the first drive means to transfer a predetermined length of zipper strip to the second conveyor, to subsequently operate the blade and then operate the second conveyor for positioning the cut-off zipper strip portion transverse to the web.
Preferably the control means are adjusted to let both conveyors move at the same speed during the supply of the length of zipper strip.
It is preferred here that the retaining means of the first and the second conveyors as well are controlled by the control means, preferably for continuously activating them. They may be designed as vacuum band meansxe2x80x94known per sexe2x80x94. In view of efficiency of the suction and creating as few as possible process disrupting air flows, it is advantageous when the machine is provided with means for adjusting the active length of the vacuum means for the second conveyor. Preferably the control means are then provided with means for comparing an entered zipper strip length and the position in transverse direction to the web and the adjusted length of the vacuum means, and of means for releasing the drive of the machine based on the outcome of said comparison. When the length of the vacuum means does not correspond to the one necessary for the process in question the machine will not be released.
The means for adjusting the active length of the vacuum means preferably comprise a tube to be connected to a vacuum source, which tube in its circumference is provided with series of apertures of different length extending in tube direction, and which is rotatable in an adjustable manner to let a selected series of apertures form the connection between the apertures in the vacuum band and the tube.
It is further preferred that at least the second conveyor is placed below the web. This improves the stability of the zipper strip.
The controllability of the zipper strip is further improved when the machine is furthermore provided with means for guiding the zipper strip on the first and/or second conveyor, which guiding means are preferably formed by a rigid guiding strip, which is positioned to extend between the male and female parts of the zipper strip. In this way the zipper strip is guided in sideward direction, so that it is prevented that it would want to run off from the conveyors as a result of its natural inclination to warp in the main plane.
Preferably the guiding strip is interrupted, and it is particularly formed by a series of teeth, so that frictional forces, that may counteract a smooth supply of the zipper strip, are limited to a minimum. The guidance is improved when the teeth have inclined side edges and/or rounded tips.
As a result of the interrupted guidance, in particular the teeth, the negative effects of the undulation in the zipper strip, which undulation is the result of the rolled-up position in which the zipper strip material is supplied, is further reduced, because of reduction of the friction and the guidance in the vertical plane. As a result the grip of the retaining means, particularly the vacuum means is improved.
Preferably the guiding strip is positioned toxe2x80x94considered in process path-engage the upstream side of the zipper strip, between the strip members having the male and female parts.
In a further development the zipper strip applicator device is also provided with an anvil strip for use in the pre-sealing of the zipper strip to the web, which anvil strip then is preferably situated at thexe2x80x94considered in process pathxe2x80x94downstream side of the second conveyor. The applicator device here also provides a counter force during the pre-sealing.
In a further development the zipper strip applicator device is supported on an auxiliary frame, which itself is supported in a main frame of the machine, the auxiliary frame with respect to the main frame being moveable between a retracted operative position and an extended adjustment position. The initial insertion of the zipper strip can then take place in an easily accessible manner. It is preferred here that a calibration is provided on the second conveyor, extending along the retaining means, preferably starting at the location of the blade.
When the machine is further provided with control means that have been provided with means for noticing the operative position of the auxiliary frame and with means for releasing the drive of the machine based on that observation, it is ensured that only in case of a correct position of the auxiliary frame and thus of the applicator device the machine can start running.
From a further aspect the invention provides a form-fill-seal machine comprising means for moving a web of packaging material through the machine according to a process path and means for transforming the web into filled bags, further comprising a zipper strip applicator device having means for supplying a zipper strip for each bag transverse to the process path, which zipper strip applicator device is supported on an auxiliary frame, which itself is supported in a main frame of the machine, the auxiliary frame with respect to the main frame being moveable between a retracted operative position and an extended adjustment position.
From another aspect the invention provides a form-fill-seal machine of the type described in the preamble, further provided with control means having means for noticing the position of a longitudinal edge of the web with respect to a fixed reference in the machine. This also provides a condition for further optimizing the accuracy of the placement of the zipper strip. It may also be possible in this way to influence the position in transverse direction of the web with respect to the form shoulder.
In a further development hereof the machine is also provided with means for positioning the zipper strip applicator device in transverse direction, in response to the data from the edge noticing means. By thus watching the position of the web side and automatically correcting the position of the applicator, errors in the width-positioning of the zipper strip with respect to the web edge as a result of sideward movement of the web is prevented. The means for positioning the zipper strip applicator device in transverse direction may be formed by a servo-driven spindle motor.
In another further development the control means are adapted to control the drive of in particular the second conveyor in the movement of the zipper strip to be applied, in response to the data from the edge noticing means.
From yet another aspect the invention provides a form-fill-seal machine of the type described in the preamble, furthermore provided with control means having first means for noticing longitudinal marks on the web and for measuring the web distance travelled over a certain period by the web at that location, which are placed near the zipper strip applicator device, at least for the noticing means at a distance from it known to the control means, the control means being adapted to control the drive(s) of the zipper strip applicator device, such as the said first and second conveyor, in response to the data from the first means for noticing longitudinal marks on the web and for measuring the web distance.
From a further aspect the invention provides a form-fill-seal machine of the type mentioned in the preamble, furthermore provided with control means having first means for noticing longitudinal marks on the web and for measuring the web position, which are placed near the zipper strip applicator device, wherein downstream of said first means the machine is provided with an end roll for the web, which is movably arranged on the machine and which can be adjusted in position with respect to the web course by means of movement means, the control means being adapted for controlling the movement means of the end roll for altering the web length between the first means and the transverse sealing means, in response to the data from the first means for noticing longitudinal marks on the web and the measuring of the web position. The end roll may be automatically moved, for instance by sliding or turning away, to increase or reduce the web length between zipper strip applicator device and transverse sealing unit/cutting unit. In this way an accurate placement of the zipper strip with respect to the tracer spot and the transverse seam is ensured again and again.
Preferably the control means are provided with means for storage of data regarding the bag length, the distance between the noticing means and the pre-seal unit for the zipper strip, the distance between the longitudinal mark and the transverse seam of a bag made and the distance between the end transverse sealing means for the zipper strip and the blade for the bags.
Alternatively described the application provides a form-fill-seal machine comprising means for moving a web of packaging material through the machine according to a process path from a web supply side and means for transforming the web into filled bags, further provided with control means having first means for noticing longitudinal marks on the web and for measuring the web position, the control means being provided with means for storage of data regarding the bag length, the machine being provided with an end or turn roll for the web, which is movably arranged on the machine in web direction and which is adjustable in position in web direction by means of movement means, the control means being adapted for controlling the movement means of the end roll for altering the length the web has to travel from the supply side to the forming means, in response to the data from the bag length input and the first means for noticing longitudinal marks on the web and measuring the web position.
Alternatively described the patent application provides a form-fill-seal machine comprising means for moving a web of packaging material through the machine according to a process path from a web supply side and means for transforming the web into filled bags, further provided with control means having first means for noticing longitudinal marks on the web and for measuring the web speed, the control means being provided with means for storage of data regarding the bag length, the machine being provided with an end or turn roll for the web, which is movably arranged on the machine in web direction and which is adjustable in position in web direction by means of movement means, the control means being adapted for controlling the movement means of the end roll for altering the length the web has to travel from the supply side to the forming means, in response to the data from the bag length input and the first means for noticing longitudinal marks on the web and measuring the web speed.
From yet a further aspect the invention provides a form-fill-seal machine comprising means for moving a web of packaging material through the machine according to a process path from a web supply side and means for transforming the web into filled bags, further comprising a zipper strip applicator device having means for supplying a zipper strip for each bag transverse to the process path and having means for sealing a zipper strip to the web for each bag to be made, the machine being adapted for making the bags with continuous web supply over the forming means, the machine being provided with means for keeping the web still at the location of the sealing means, and with means placed downstream of the sealing means for forming a buffer web length prior to each keeping still and releasing it during keeping the web still. Thus a reliable, continuous web supply to the moulding and closing means is ensured.
It is preferred here that the end roll and its movement means are a part of the buffer forming means, so that it can be effective in two ways.
From another aspect the invention provides a form-fill-seal machine comprising means for moving a web of packaging material through the machine according to a process path and means for transforming the web into filled bags, further comprising a zipper strip applicator device having means for supplying a zipper strip for each bag transverse to the process path, which supply means comprise a first and a second conveyor, which in supply direction of the zipper strip are placed one behind the other and are both provided with means for retaining the zipper strip during supply, a blade being placed between the first and second conveyor for cutting the zipper strip. Both conveyors can be driven by one single drive, the transfer to the second conveyor for instance being such that this one runs a little faster than the first conveyor, so that the zipper strip is stretched during positioning.
Preferably the first and the second conveyor are positioned to support the zipper strip.
Preferably the retaining means are vacuum means.
From a further aspect the application provides a form-fill-seal comprising means for moving a web of packaging material through the machine according to a process path and means for transforming the web into filled bags, further comprising a zipper strip applicator device having means for supplying a zipper strip for each bag transverse to the process path, which supply means comprise a conveyor positioned transverse to the process path, which is positioned to support the zipper strip and is provided with means for retaining the zipper strip during the supply and pre-sealing at the lower side of the web. The support of the zipper strip improves its stability during supply and positioning, so that the zipper strip can be accurately applied.
It is noted that measures discussed above, such as web side watcher, the end roll and the adjustment means for the active length of the vacuum band, can be used both in an arrangement with two conveyors and in an arrangement with one continuous conveyor.
From a further aspect the application provides a form-fill-seal machine comprising means for moving a web of packaging material through the machine according to a process path and means for transforming the web into filled bags, further comprising a zipper strip applicator device having means for supplying a zipper strip for each bag transverse to the process path, which supply means comprise a conveyor positioned transverse to the process path, furthermore provided with means for permanently adhering both the strip members provided with male and female parts respectively of the zipper strip, at locations that are situated at a mutual distance corresponding to the desired length of the cut-off zipper strips to the applied, the adhering means comprising two adhering members, which engage on both sides of the male and female parts to seal them to each other. In this way a bulge in the zipper strip ends is prevented, which is favourable to the manageability in the further process. The so-called xe2x80x9ccrunchingxe2x80x9d can now take place with a running zipper strip. By adapting the control means at the wanted strip length and with the known distance between blade and crunch unit, as well as with known supply speed of the zipper strip, the correct moment for crunching can be automatically determined and at that moment the crunch unit can be activated.
Preferably two adhering members are positioned to enclose the male and female parts between them during sealing.
It is further preferred here that the two adhering members comprise a rotatable or idle anvil and a sealing arm, particularly ultrasonic sealing arm. The freely rotatable anvil prevents unwanted frictional forces and the arm is only in contact with the strip when crunching has to take place.
From a further aspect the invention provides a form-fill-seal machine comprising means for moving a web of packaging material through the machine according to a process path and means for transforming the web into a tubular shape, turning it into bags, filling the bags and closing the filled bags, the means for transforming into the tubular shape comprising longitudinal guides, placed at a mutual distance corresponding to the zipper strip length, for guiding the tube from the transformation means to the location of filling. Preferably the filling means comprise a chute, which at the outside is provided with longitudinal guides. Thus it is prevented that the tubular web twists and the zipper strip would not lie correctly any more and no good transverse seal could be made. Because of the longitudinal guides the largest circumferential size of the chute is not changed, but the strips lie within said circumferential size.